Motor

ABSTRACT

A yoke of a motor has a bottom and an open end and accommodates an armature. An end bracket substantially closes the open end of the yoke. A connector portion, which bulges outward of the yoke, and a cutout portion are formed in the circumferential wall of the end bracket. A pair of feed members is provided to extend from the interior of the end bracket to the connector portion through the cutout portion. The end bracket has an accommodation recess for accommodating the noise suppression element at a position corresponding to the cutout portion. Each feed member has an accommodation recess corresponding portion, which corresponds to the accommodation recess, and a cutout portion corresponding portion, which corresponds to the cutout portion. The distance between the accommodation recess corresponding portions of the feed members is greater than the distance between the cutout portion corresponding portions.

BACKGROUND OF THE INVENTION

The present invention relates to a motor in which noise suppressionelements can be installed.

Conventionally, a type of motor has been known that includes anarmature, a substantially cylindrical yoke that has a bottom and an openend and rotationally receives an armature, an end bracket secured tosubstantially close the open end of the yoke, and noise suppressionelements such as capacitors provided in the end bracket. For example,the motor disclosed in Japanese Laid-Open Patent Publication No.2009-112095 has a connector portion formed on a part of thecircumferential wall of the end bracket. The connector portion bulgesoutward from the yoke when viewed in the axial direction. A cutoutportion is formed in a part of the circumferential wall of the endbracket that corresponds to the connector portion. The cutout portionallows the interior of the end bracket to communicate with the connectorportion. A pair of feed members extends from the interior of the endbracket to the connector portion through the cutout portion. The feedmembers have a pair of cutout portion corresponding portions, whichcorrespond to the cutout portion. Noise suppression elements are locatedbetween the cutout portion corresponding portions. The terminals of thenoise suppression elements are drawn outward in the radial direction andconnected to the feed members at the connector portion.

However, in the motor described above, the noise suppression elementsare located between the cutout portion corresponding portions, whichcorrespond to the cutout portion of the feed members. Therefore, thewidth of the cutout portion (discontinued part of the circumferentialwall), at which the cutout portion corresponding portions are located,is increased. At this part, the strength of the end bracket is reduced.Therefore, to ensure the strength of the end bracket, the thickness ofthe end bracket needs to be increased in parts in the vicinity of acutout portion.

Accordingly, it is an objective of the present invention to provide amotor that has a cutout portion with a reduced width and thereforeeasily ensures the strength of an end bracket.

To achieve the foregoing objective and in accordance with one aspect ofthe present invention, a motor including an armature, a substantiallycylindrical yoke, and an end bracket is provided. The yoke has a bottomand an open end. The yoke rotationally accommodates the armature. Theend bracket is fixed to the yoke to substantially close the open end ofthe yoke. The end bracket has a radial direction, a circumferentialdirection, and an axial direction. A connector portion is formed in apart of a circumferential wall of the end bracket, the connector portionbulging outward from the yoke as viewed in the axial direction. A cutoutportion is formed in a part of the circumferential wall of the endbracket that corresponds to the connector portion. The cutout portionallows the interior of the end bracket to communicate with the connectorportion. A pair of feed members is provided to extend from the interiorof the end bracket to the connector portion through the cutout portion.A pair of terminals of a noise suppression element can be connected tothe feed members, respectively. The end bracket has an accommodationrecess for accommodating the noise suppression element at a positioncorresponding to the cutout portion. The circumferential width of theaccommodation recess is greater than the circumferential width of thecutout portion. Each feed member has an accommodation recesscorresponding portion, which corresponds to the accommodation recess,and a cutout portion corresponding portion, which corresponds to thecutout portion. The distance between the accommodation recesscorresponding portions of the feed members is greater than the distancebetween the cutout portion corresponding portions.

Other aspects and advantages of the invention will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1A is a partial plan view illustrating a motor according to oneembodiment of the present invention;

FIG. 1B is a cross-sectional view taken along line 1B-1B in FIG. 1A;

FIG. 2 is a partial plan view showing the motor of FIG. 1A before arotational speed detecting member is installed;

FIG. 3 is a partial plan view for explanatory illustration of the endbracket in the motor of FIG. 1A;

FIGS. 4A to 4D are explanatory diagrams showing the feed members in themotor of FIG. 1A;

FIG. 5A is a partial plan view illustrating a motor of a differentspecification; and

FIG. 5B is a cross-sectional view taken along line 5B-5B in FIG. 5A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of the present invention will now be described withreference to the drawings.

As shown in FIGS. 1A and 1B, a motor 1 includes a substantiallycylindrical yoke 2, which has a bottom and an open end, and an endbracket 3, which is fixed to substantially close the open end of theyoke 2. The yoke 2 is made of magnetic metal. Magnets, which are notillustrated, are fixed to the inner circumferential surface of the yoke2. An armature is accommodated in the yoke 2. A rotary shaft 4 of thearmature is rotationally supported by a bearing 5 held at the bottom ofthe end bracket 3 and an unillustrated bearing, which is heldsubstantially at the center of the bottom of the yoke 2, that is, acenter of an end face opposite to the open end. In addition to a coreabout which coils are wound, a commutator and a sensor magnet 6 (referto FIG. 1B) are fixed to the rotary shaft 4. As shown in FIG. 1B, thesensor magnet 6 of the present embodiment is fixed to the rotary shaft 4at a position that is displaced from the bearing 5 in the axialdirection and in the vicinity of the bearing 5.

The end bracket 3 is made of plastic and is shaped as a cylinder havinga bottom and an open end corresponding to the open end of the yoke 2. Athrough hole 3 a is formed through a center of the bottom of the endbracket 3 in the axial direction to receive the distal end of the rotaryshaft 4. The bearing 5 is held at a part of the through hole 3 a that iscloser to the interior of the yoke 2. The distal end of the rotary shaft4 is coupled to a coupler portion (not shown) of a load.

A connector portion 3 b is integrally formed with a part of thecircumferential wall of the end bracket 3. The connector portion 3 bbulges outward of the yoke 2 when viewed in the axial direction of therotary shaft 4, that is, in the axial direction of the end bracket 3. Acutout portion (discontinued part of the circumferential wall) is formedin a part of the circumferential wall of the end bracket 3 thatcorresponds to the connector portion 3 b. The cutout portion allows theinterior of the end bracket 3 to communicate with the connector portion3 b. The connector portion 3 b has a cylindrical portion 3 d. Thecylindrical portion 3 d extends in the axial direction to receive anexternal connector of a control device (not shown), which serves as apower source device. In FIG. 1B, the cylindrical portion 3 d extendsupward along the yoke 2.

As shown in FIG. 3, the end bracket 3 has an accommodation recess 3 e ata position corresponding to the cutout portion 3 c. The width of theaccommodation recess 3 e in a direction perpendicular to the radialdirection, that is, in the circumferential direction, is greater thanthat of the cutout portion 3 c. The accommodation recess 3 e is formedsubstantially as a rectangle, which is formed by parallel two sidesextending in the radial direction as viewed in the axial direction andanother two sides extending in a direction perpendicular to the radialdirection to connect the first two sides. The accommodation recess 3 eis recessed in the axial direction, or a in a direction away from theviewer of FIG. 3.

As shown in FIG. 1A, the end bracket 3 has a pair of feeder brushes,which is located inward of the yoke 2 as viewed in the axial directionand held to be movable in the radial direction. In the presentembodiment, the pair of feeder brushes includes first and second feederbrushes 11, 12. The end bracket 3 has an unillustrated torsion coilspring, which urges and presses the feeder brushes 11, 12 radiallyinward against the commutator. As shown in FIGS. 2 and 3, the endbracket 3 has a pair of feed members, or first and second feed members21, 22. The first and second feed members 21, 22 are electricallyconnected to the feeder brushes 11, 12, respectively, and extend, asviewed in the axial direction, from the interior of the yoke 2 to theconnector portion 3 b (the cylindrical portion 3 d) through the cutoutportion 3 c.

Specifically, a pigtail 11 a of the first feeder brush 11 is connectedto the first feed member 21 via a choke coil 23 and a plate-likethermistor 24 as shown in FIGS. 4A and 4B. A pigtail 12 a of the secondfeeder brush 12 is connected to the second feed member 22 via a chokecoil 25 as shown in FIGS. 4C and 4D. As shown in FIGS. 2 and 3, the feedmembers 21, 22 has accommodation recess corresponding portions 21 a, 22a, which correspond to the accommodation recess 3 e, and cutout portioncorresponding portions 21 b, 22 b, which correspond to the cutoutportion 3 c. The feed members 21, 22 extend to the cylindrical portion 3d of the connector portion 3 b. At the distal ends, the feed members 21,22 have connection terminal portions 21 c, 22 c extending in the axialdirection and along the cylindrical portion 3 d. With the feed members21, 22 installed in the end bracket 3 as shown in FIGS. 2 and 3, thedistance between the accommodation recess corresponding portions 21 a,22 a is greater than the distance between the cutout portioncorresponding portions 21 b, 22 b. Further, as shown in FIGS. 1B and 3,with the feed members 21, 22 installed in the end bracket 3, theaccommodation recess corresponding portions 21 a, 22 a are flush withinner surfaces 3 f of the accommodation recess 3 e, which face eachother in the width direction. As shown in FIG. 1B, axial ends (lowerends as viewed in FIG. 1B) of the accommodation recess correspondingportions 21 a, 22 a are arranged to contact in the axial directionopening edge (the upper end as viewed in FIG. 1B) of the accommodationrecess 3 e of the end bracket 3. The accommodation recess correspondingportions 21 a, 22 a at least partly overlap with the bearing 5 in theaxial direction (see FIG. 1B).

First and second noise suppression elements 31, 32 have a pair ofterminals 31 a and a pair of terminals 32 a, respectively. Connectionnotches 21 d, 21 e, 22 d, 22 e, which serve as connection portions, areformed in the accommodation recess corresponding portions 21 a, 22 a ofthe feed members 21, 22. The terminals 31 a, 32 a of the first andsecond noise suppression elements 31, 32 are connected to the connectionnotches 21 d, 21 e, 22 d, 22 e. Specifically, the accommodation recesscorresponding portions 21 a, 22 a have the connection notches 21 d, 21e, 22 d, 22 e, each of which receives one of the terminals 31 a, 32 a ofthe noise suppression elements 31, 32. The connection notches 21 d, 21e, 22 d, 22 e are arranged in parallel in the radial direction of thefeed members 21, 22. The connection notches 21 d, 21 e, 22 d, 22 e ofthe present embodiment have shapes capable of receiving in the axialdirection the terminals 31 a, 32 a of the first and second noisesuppression elements 31, 32.

The first noise suppression element 31 of the present embodiment isformed by a pair of combined capacitors 31 b. The capacitors 31 b areheld by a holding member 31 c such that the flat surfaces thereof faceeach other. Each capacitor 31 b has first and second terminals. Thefirst terminals are connected to the holding member 31 c. The secondterminals are drawn in the direction opposite to the facing directionand function as terminals 31 a for external connection of the firstnoise suppression element 31. A ground terminal 31 d is formed in theholding member 31 c. With the first noise suppression element 31installed in the end bracket 3, the ground terminal 31 d is tightly heldbetween the end bracket 3 and the yoke 2. The second noise suppressionelement 32 of the present embodiment is formed by a single varistor. Themain body of the second noise suppression element 32 except for theterminals 32 a can be arranged between the flat surfaces the capacitors31 b.

Each of the connection notches 21 d, 21 e, 22 d, 22 e has a width (inthe radial direction) that corresponds to the size of the correspondingone of the terminals 31 a, 32 a of the noise suppression elements 31,32. Also, the widths of the connection notches 21 d, 21 e, 22 d, 22 eare determined to allow the terminals 31 a, 32 a to be press fitted inthe connection notches 21 d, 21 e, 22 d, 22 e. The connection notches 21d, 21 e, 22 d, 22 e are formed in the feed members 21, 22 to extend inthe axial direction, and open in one end in the axial direction of thefeed members 21, 22. The width of the opening of each connection notches21 d, 21 e, 22 d, 22 e widens toward the open end. The first and secondnoise suppression elements 31, 32 are accommodated in the accommodationrecess 3 e as shown in FIGS. 1B and 2. In this state, the terminals 31a, 32 a are press fitted in and supported by the connection notches 21d, 21 e, 22 d, 22 e to be electrically connected to the connectionnotches 21 d, 21 e, 22 d, 22 e.

As shown in FIGS. 5A and 5B, the connection notches 21 d, 22 d of thepresent embodiment have such shapes to which a terminal 41 a of a noisesuppression element 41 in a motor having a different specification canbe inserted (press-fitted). The noise suppression element 41 is formedby a single capacitor and is suitable for motors having inexpensivespecifications without varistors.

As shown in FIGS. 1A and 1B, a rotational speed detecting member 51 isattached to the end bracket 3 at a position facing the sensor magnet 6in the radial direction. The rotational speed detecting member 51detects changes in the magnetic force of the sensor magnet 6, that is,the number of rotations of the rotary shaft 4.

Specifically, the rotational speed detecting member 51 includes aplastic base member 51 a, a pair of sensor terminals 51 b insert moldedin the base member 51 a, and a Hall IC 51 c mounted on a substrate 51 d.The substrate 51 d is fixed to the base member 51 a. As shown in FIG.1B, the rotational speed detecting member 51 is located at a positiondisplaced in the axial direction from the accommodation recesscorresponding portion 22 a (21 a). As shown in FIG. 1A, the rotationalspeed detecting member 51 substantially covers the accommodation recess3 e (the first and second noise suppression elements 31, 32) as viewedin the axial direction. The Hall IC 51 c (the substrate 51 d) is locatedin a part of the rotational speed detecting member 51 that faces thesensor magnet 6 (the center axis).

The rotational speed detecting member 51 has an extension 51 e, whichextends to the connector portion 3 b through the cutout portion 3 c.When the rotational speed detecting member 51 is installed in the endbracket 3, the extension 51 e is located at a position displaced in theaxial direction from the cutout portion corresponding portions 21 b, 22b of the feed members 21, 22 and overlaps the cutout portioncorresponding portions 21 b, 22 b as viewed in the axial direction. Thesensor terminals 51 b are embedded in the extension 51 e. A first end ofeach sensor terminal 51 b is connected to the substrate 51 d. A secondend of each sensor terminal 51 b protrudes in the axial directiontogether with (parallel with) the connection terminal portions 21 c, 22c of the feed members 21, 22 in the cylindrical portion 3 d. When anexternal connector is plugged into the cylindrical portion 3 d, thesecond ends of the sensor terminals 51 b are connected to the controldevice together with the connection terminal portions 21 c, 22 c.

Operation of the motor 1 will now be described.

When the external control device supplies a drive current to the coilsof the armature via the feed members 21, 22, the feeder brushes 11, 12,and the commutator, the armature is rotated. When the sensor magnet 6rotates together with the rotary shaft 4 of the armature, theaccompanying change in the magnetic force is detected by the rotationalspeed detecting member 51 (the Hall IC 51 c), a signal corresponding tothe number of rotations of the rotary shaft 4 is output to the controldevice. Various control processes are executed in accordance with thesignal. During the operation, the first and second noise suppressionelements 31, 32 connected to the feed members 21, 22 remove noise.

The above described embodiment has the following advantages.

(1) A cutout portion is formed in a part of the circumferential wall ofthe end bracket 3 that corresponds to the connector portion 3 b. Thecutout portion allows the interior of the end bracket 3 to communicatewith the connector portion 3 b. The accommodation recess 3 e foraccommodating the first and second noise suppression elements 31, 32 isformed at a position in the end bracket 3 that corresponds to the cutoutportion 3 c. The width of the accommodation recess 3 e in a directionperpendicular to the radial direction, that is, in the circumferentialdirection, is greater than that of the cutout portion 3 c.

With the feed members 21, 22 installed in the end bracket 3, thedistance between the accommodation recess corresponding portions 21 a,22 a, which correspond to the accommodation recess 3 e, is greater thanthe distance between the cutout portion corresponding portions 21 b, 22b, which correspond to the cutout portion 3 c. According to thisconfiguration, compared to a conventional motor, in which noisesuppression elements are located between cutout portion correspondingportions, which correspond to cutout portions of feed members, thestrength of the end bracket 3 is easily ensured while reducing the widthof the cutout portion 3 c (discontinued part of the circumferentialwall) to reduce the thickness, for example, of the end bracket 3.

(2) With the feed members 21, 22 installed in the end bracket 3, theaccommodation recess corresponding portions 21 a, 22 a are flush withinner surfaces 3 f, which are arranged in the width direction of theaccommodation recess 3 e. The connection notches 21 d, 21 e, 22 d, 22 eare formed in the accommodation recess corresponding portions 21 a, 22a. The terminals 31 a, 32 a of the first and second noise suppressionelements 31, 32 are connected to the connection notches 21 d, 21 e, 22d, 22 e. Thus, the terminals 31 a, 32 a of the first and second noisesuppression elements 31, 32 can be shortened and easily connected. Thatis, since the accommodation recess corresponding portions 21 a, 22 a ofthe feed members 21, 22 are arranged to extend the inner surfaces 3 f ofthe accommodation recess 3 e in the axial direction, the accommodationrecess 3 e is not narrowed due to the accommodation recess correspondingportions 21 a, 22 a. The terminals 31 a, 32 a of the first and secondnoise suppression elements 31, 32 accommodated in the accommodationrecess 3 e do not need to prolonged to each the connection notches 21 d,21 e, 22 d, 22 e of the accommodation recess corresponding portions 21a, 22 a, and the terminals 31 a, 32 a of the first and second noisesuppression elements 31, 32 can be easily connected.

(3) A plurality of parallel connection notches 21 d, 21 e, 22 d, 22 eare formed in the radial direction in the accommodation recesscorresponding portions 21 a, 22 a of the feed members 21, 22. Theterminals 31 a, 32 a of the first and second noise suppression elements31, 32 are connected to the connection notches 21 d, 21 e, 22 d, 22 e.Therefore, when the first and second (a plurality of) noise suppressionelements 31, 32 are located between the feed members 21, 22, theterminals 31 a, 32 a of the first and second (a plurality of) noisesuppression elements 31, 32 can be easily connected to each other. Theterminals 31 a, 32 a of the first and second noise suppression elements31, 32 do not need to be extended, but can be shortened.

(4) The accommodation recess corresponding portions 21 a, 22 a arelocated at positions where the axial dimensions thereof are equal tothat of the bearing 5, and displaced axially from the position of therotational speed detecting member 51. Therefore, the accommodationrecess corresponding portions 21 a, 22 a do not need to be formed toavoid (detour) the rotational speed detecting member 51 as viewed in theaxial direction. This allows the feed members 21, 22 to be shortened.

(5) In the rotational speed detecting member 51, the extension 51 e,which extends to the connector portion 3 b via the cutout portion 3 c,is located at a position axially displaced from the positions of thecutout portion corresponding portions 21 b, 22 b of the feed members 21,22. Therefore, the cutout portion corresponding portions 21 b, 22 b donot need to be formed to avoid (detour) the extension 51 e as viewed inthe axial direction. This allows the width of the cutout portion 3 c(discontinued part of the circumferential wall) to be further reduced.Thus, the strength of the end bracket 3 is easily ensured while reducingthe thickness, for example, of the end bracket 3.

The above described embodiment may be modified as follows.

In the above illustrated embodiment, the accommodation recesscorresponding portions 21 a, 22 a of the feed members 21, 22 are flushwith the inner surfaces 3 f, which are arranged in the width directionof the accommodation recess 3 e. However, the present invention is notlimited to this configuration. The accommodation recess correspondingportions 21 a, 22 a may be displaced from the inner surfaces 3 f asviewed in the axial direction.

In the above illustrated embodiment, a plurality of (two) parallelconnection notches 21 d, 21 e, 22 d, 22 e are formed in the radialdirection in the accommodation recess corresponding portions 21 a, 22 a.However, the present invention is not limited this configuration. Forexample, only one connection notch (connection portion) may be formed ineach of the accommodation recess corresponding portions 21 a, 22 a. Inthis case, only one noise suppression element can be provided(connected). Also, the number of connection notches (connectionportions) in the motor may be increased, so that three or more noisesuppression elements can be provided.

In the above illustrated embodiment, the accommodation recesscorresponding portions 21 a, 22 a are located at positions where theaxial dimensions thereof are equal to that of the bearing 5, anddisplaced axially from the position of the rotational speed detectingmember 51. However, the present invention is not limited to this. Thatis, the accommodation recess corresponding portions 21 a, 22 a may belocated at positions that are aligned with the rotational speeddetecting member 51 in the axial direction.

In the rotational speed detecting member 51, the extension 51 e, whichextends to the connector portion 3 b via the cutout portion 3 c, islocated at a position axially displaced from the positions of the cutoutportion corresponding portions 21 b, 22 b of the feed members 21, 22.However, the present invention is not limited to this. That is, theextension 51 e may be located at a position that is aligned with thecutout portion corresponding portions 21 b, 22 b in the axial direction.

In the above embodiment, the connection portions are formed by theconnection notches 21 d, 21 e, 22 d, 22 e, into which the terminals 31a, 32 a of the first and second noise suppression elements 31, 32 can beinserted in the axial direction. However, connection portions havingdifferent shapes may be used as long as connection terminals aredesigned to receive terminals.

In the above described embodiment, the widths of the connection notches21 d, 21 e, 22 d, 22 e are determined such that the terminals 31 a, 32 acan be press fitted in the corresponding the connection notches 21 d, 21e, 22 d, 22 e. However, the present invention is not limited to thisconfiguration. That is, the width may be determined such that theterminals 31 a, 32 a can be press fitted into part of the connectionnotches. For example, the widths of the connection notches may bedetermined such that the terminals 31 a, 32 a cannot be press fitted inany of the connection notches. In a case where press fitting cannot beperformed, soldering needs to be performed, instead.

1. A motor comprising: an armature; a substantially cylindrical yokehaving a bottom and an open end, the yoke rotationally accommodating thearmature; and an end bracket that is fixed to the yoke to substantiallyclose the open end of the yoke, the end bracket having a radialdirection, a circumferential direction, and an axial direction, whereina connector portion is formed in a part of a circumferential wall of theend bracket, the connector portion bulging outward from the yoke asviewed in the axial direction, a cutout portion is formed in a part ofthe circumferential wall of the end bracket that corresponds to theconnector portion, wherein the cutout portion allows the interior of theend bracket to communicate with the connector portion, a pair of feedmembers is provided to extend from the interior of the end bracket tothe connector portion through the cutout portion, wherein a pair ofterminals of a noise suppression element can be connected to the feedmembers, respectively, the end bracket has an accommodation recess foraccommodating the noise suppression element at a position correspondingto the cutout portion, wherein the circumferential width of theaccommodation recess is greater than the circumferential width of thecutout portion, and each feed member has an accommodation recesscorresponding portion, which corresponds to the accommodation recess,and a cutout portion corresponding portion, which corresponds to thecutout portion, wherein the distance between the accommodation recesscorresponding portions of the feed members is greater than the distancebetween the cutout portion corresponding portions.
 2. The motoraccording to claim 1, wherein the accommodation recess correspondingportions are formed to be flush with a pair of inner surfaces facingeach other in the width direction of the accommodation recess, andwherein each accommodation recess corresponding portion has a connectionportion, to which a terminal of the noise suppression element isconnected.
 3. The motor according to claim 1, wherein each accommodationrecess corresponding portion has a plurality of connection portions,wherein each of a pair of terminals of each of a plurality of noisesuppression elements is connected to each connection portion, and theconnection portions are formed in the feed member and arranged in theradial direction.
 4. The motor according to claim 1, wherein the endbracket holds a bearing for supporting a rotary shaft of the armature, asensor magnet is fixed to the rotary shaft at a position displaced inthe axial direction from the bearing, a rotational speed detectingmember is attached to the end bracket at a position facing the sensormagnet in the radial direction, the rotational speed detecting member iscapable of detecting changes in the magnetic force of the sensor magnet,and the accommodation recess corresponding portion at least partlyoverlaps with the bearing in the axial direction and is displaced fromthe rotational speed detecting member in the axial direction.
 5. Themotor according to claim 4, wherein the rotational speed detectingmember has an extension that extends to the connector portion via thecutout portion, and the extension is located at a position displaced inthe axial direction from the cutout portion corresponding portions ofthe feed members.